Centrifugal separator



3 sheets-sheet 1 F. H. SMITH CENTRIFUGALSEPARATOR Dec. 23, 1952 Filed sept. 1e, 194s ATTORNEYS Dec. 23, 1952 SMITH CENTRIF'UGAL SEPARATOR Filed Sept. 16, 1948 3 Sheets-Sheet 2 INVENTOR.

FREDERICK H.SM|TH Amador/?,

ATTORNEYS Dec. 23, 1952 F. H. sMrrH 2,622,794

CENTRIFUGAL SEPARATOR Filed Sept. 16, 1948 3 Sheets-Sheet 3 INVENTOR.

FREDERIC K H SMITH ATTORNEYS Patented Dec. 23, 1952 PATENT OFFICE .CENTRIFUGAL SEPART'OR Delaware Application'seltember 16, 1948,`Se1i'al' No. 49:605

(Cl. '23S-J7) Ir4f(llaims. 1

vThis invention relates to centrifugal apparatus adapted `for 'the separation or yclarification of mixtures of liquids "and solids, and "has to 'do more particularly "with an improved voontinucuis Ytype o'fhorizon'tal centrifuge.

'Horizontal lcentrifuges utilizing a `scroll 'or 'helical screw -to `Tconvey the solids in the `opposite direction from fthe liquid I"il'ow Within `:the centrifuge are well known. Likewise, centrifuges utilizing a'stack of discsmcomprisedo'f a plurality of Iclosely vspaced conical J"members which act fas "the separating `or "clarifying element r'are also Well '-known. The scroll is independently journaled from the rotorforbovvl since -thescro'll rotates 'at fa slightly reduced speed in order to provide the 'scrolling action.

The 'scroll type o'f centrifuge is adapted for relatively large volumes and high percentage of solids Whereas thefdisc type ofcentrifug'e is utilized for c'its v`higherclarification efliciency 'but the conventional disc machine cannot ordinarily 'be used for continuous operation because of its tendency to `plug Aafter comparatively limited periods A.of use. The above disadvantages are especially critical Afor certain materials and in certain chemical .extraction processes. 'The solids linithe centrifuge frequency `are not suincien'tly plastic to 'be ejected 4through Vthe 'fine nozzlesemploye'd with a -ldis'c .type 'centrifuge and as mentioned above theso'lid's f'ares'fre'quently too large in volume'to .be handled in the disc machine under 'continuous operation.

Nevertheless, such continuous operation is highly desirable in many chemical processes 'in order to handle the relatively large Aquantities of material involved. Furthermore, 'a 'disc type of machine is valso vdesirable to obtain 'satisfactory clarication. Therefore, in order to provide a continuous machine which "has the required clarification -`it Ais desirable fto incorporate an efiicient scroll :in jthe disc centrifuge.

The 'problems involved in providing 'a satisfactory scroll .for 'a disc centrifuge arenot, however, simple of solution. In the rst place, the .overall diameter of the machine should be kept at a minimum. In the second place, the rscroll 'must have controlled Aclearance with theside of the bowlfbutat thesametime there must berno scraping-between .the-:scroll and the bowl. This condition Would-of coursecause excessive wear. Further-more, .the high `stresses involved -due to centrifugal vforce require tha-t a rigid lconstruction be employed which has aiminimum of weight but `at the same time is strong enough to :prevent failure at the relatively high speeds employed with disc centrifuges.

Aiprimary object, therefore, of theinven-tionis to provide in .horizontal centrifuge construction, acornbined disc scroll rotor assembly.

Astill further object is to provide in va machine of this type an improved discstack.

still further object is toprovide in a machine of 4thistype an improved conveyor body-assembly on which both the disc stacks and the `scroll may be mounted.

A1 still further Objectis lto 'provide ina machine of this ltype a 'conveyor vassembly so fabricated as to have ample .radialrigidity and strength to carry `.the :high loads imposed by 'the 'centrifugal force o'f'the combined scroll yand stacks.

A stillf'further object is to .provide in a machine of this ity-pe a'scroll rotating at slight differential speed'whichis at the same time mounted on the conveyor `body rather 'than independently ,journaled.

`A stil'l further object .is to provide in a machine of this 'type means for avoiding plugging of the machine in zthe event lof excess feeding.

Further objects Will be apparent from the specification anddravvings in which:

Fig. lisa 4longitudinal section of a centrifuge constructed in accordance with rthe invention, as seen at I-^I of Fig. 2;

Fig. `2 is atransverse section of the structure of Fig. las'seen along the line 2-2 of Fig. l;

Fig. l3 lis a longitudinal section on a reduced scale of the -conveyer body Weldm'ent;

Fig. 4 an enlarged `detail of one of the disc stack assemblies;

Fig. r5 is Ia section taken on the line 5--5 of Fig. 14;

Fig. 6 is :an end elevation yof the structure of Fig. 4; and

Fig. f7 is an exploded perspective on an enlarged scale `of one end of the disc stack showing the method "of assembly.

Referring nowmore particularly to the drawings, -a centrifuge constructed in accordance with `the invention bassa-stationary case IB which encloses the rotor or bowl I'I The -bowl AH `has a slightly tapered cylindrical por-tion I ia, rand a truste-conical portion vI-Ib; and it will `be understood that slurry introduced into the bowl asit is rotating-.at high zspeed is separated by the mechanisrn to `be described more fully hereinafter so that the liquid will be Withdrawn from the bowl -through .ports I2, I2, Whereas solids will be Withdrawn from 'the bowl through a plurality of ports at the opposite end of the bowl, one of which is shown at i3.

Bowl 'I I is rigidly attached at one end to adriving cap I4 which extends through case Ill and is journaled in bearings (not shown). Driving force for the bowl is supplied through the hollow shaft Illa formed integrally with cap I4. The conveyer body assembly I is independently journaled on cap I4 by means of bearing I6 to which it is connected by means of an annular collar I'I and screws I 8. Bearing l5 may be lubricated by means of a grease fitting I9 and a conventional grease retainer is provided between the conveyer body I5 and cap i4. It will be understood that conveyer body I5, collar I'I and bearing member 2l rotate at high speed with respect to casing I5 but at the same time have a slightly slower speed than that of bowl II. Bearing I6 provides for this differential movement between the bowl I I and the conveyer body I5.

The construction of the opposite end of the machine includes a cap securely bolted to the large end of bowl II by means of screws 26, 26. Cap 25, in a manner similar to cap I4, is formed integrally with a driving sleeve 25a which is mounted rotatably on a shaft 26 in order to provide the differential speed between the bowl II and the conveyer body I5. Shaft 25 extends within the conveyer body I5 and is splined to an annular thrust collar 2l which encloses thrust bearing 23. Collar 2l is secured to bearing member 2S and conveyer body sleeve 3E] by means of screws SI-SI. A suitable gasket 32 and oil seal 33 are likewise provided. It will be understood that the conveyer body is journaled radially on bearings I5 and 26 so that it is free to rotate independently in bowl II in accordance with the speed of shaft 25. A standard differential gear unit (not shown) connects sleeve 25a and shaft 25 so that driving force exerted on sleeve 25a through bowl II and sleeve I4a serves to drive conveyer body I5 in the same direction but at a speed of substantially 20-25 R. P. M. less.

Referring now more particular to Fig. 3 the conveyer body I5 comprises a weldment which has been very carefully constructed to withstand the extremely high radial stress imposed upon this assembly. It has been found highly desirable to incorporate the portion 45a of scroll 40 around the periphery of the conveyer body rather than to have it independently mounted. Otherwise the necessary scroll framework would seriously hamper the free passage of solids, and furthermore, it would occupy so much space that the over-all diameter of the machine would be greatly increased with concurrent increase in cost without any proportional gain in clarification. In the present machine the normal operating speed of the bowl is on the order of 3250 R. P. M. and the normal operating speed of the conveyer body is 3230 R. P. M.

The main conveyer body sleeve 4I is reamed at one end as shown at 42 in Fig. 3 to accept the sleeve S5. An annular ring 43 is welded around the same extremity of sleeve 4I and this ring is drilled and tapped at 44 to accommodate screws 45 (Fig. l) which retain the sleeve 30 in sleeve 4I. IThe opposite end of sleeve 4I has a cap 46 welded thereto and provided with radial milled slots 4l through which gusset plates 48 may be welded to the cap. The gusset plates 48 are also Welded to the bore of sleeve 4I to provide ample strength and rigidity. A plurality of fins 49 (in the present example 12) are then radially welded along their edges to the periphery of sleeve 4I so that the fins, when in place, substantially extend axially the length of sleeve 4 I.

The outer edge of each n is provided with a crossbar 49a which is attached to the n by means of welding through drilled holes 50, 50 in the crossbars. The purpose of this construction is to avoid any weld in the angle formed between the crossbars and the lateral faces of the fins 49 and at the same time to provide ample tensile strength between the crossbar and each fin. 'I'he section 40a of double pitch scroll 4l) is then securely welded around the outside of each crossbar as shown in Figs. 1-3, This construction is extremely rugged and utilizes both the scroll 40al as Well as the radial ns 49 as integral stress members thereby providing ample strength for the relatively concentrated mass around the periphery of conveyer body I5. Since it is essential that the disc stacks 5I, 5I must be in spaced relation to sleeve 4I as well as to scroll 40 in order to provide proper passage for the solids and liquids, a substantial mass around the periphery of the conveyer body cannot be avoided without loss of eiciency.

A second sleeve 52 is axially welded to cap 4G and similarly has a reamed bore 53 to accommodate the collar Il. Scroll 4519, likewise of double pitch, is welded around the outer periphery of sleeve 52 and is adapted to form a continuous conveying device together with scroll 40a for solids inside the bowl II. A plurality of radial feed passages 54 are welded to the outer side of cap 45 as shown in Figs. 2 and 3 and these passages terminate centrally in a circular feed chamber 55 having an axial opening 56. A fourbladed accelerator is positioned in alignment with passages 54 and serves to bring the liquid slurry up to speed in a short time. v

Referring now more particularly to Figs. 4 7, the individual disc stacks 5I comprise a pair of side members 65, having biased milled slots 6I on opposite faces of each member. The side members 65, 65' are desirably formed of a synthetic plastic material of relatively light weight. The discs 52, 62 are light weight stampings preferably of aluminum or stainless steel and have oppositely biased edges 52a and 52h. The discs 52 are also tapered so that when the stacks 5I are assembled as shown in Fig. 4, side members 60, 8c will be parallel to a radius of the conveyer body I5. In this way the assembled stacks may be supported between the fins 49 as shown in Fig. 2. In assembling the stacks 5I, the discs are inserted in the milled slots 6I, 6I whereupon the side members are attached to each other by means of pins 53, G3 (Fig. 7). In the present instance there are twelve of these individual disc stack assemblies.

The stacks 5I are adapted to be slidably mounted between fins 49 and are retained therein by means of clips 54 and screws 55 (Fig. 1). Ample clearance between the inner edge of the stacks and the periphery of sleeve 4I is provided for free passage of liquid as shown clearly in Fig. 2. The stacks are securely held in the conveyer body assembly by means of the crossbars 49a and the radial taper of the lateral faces of the ns 49, 49.

In operation-the liquid slurry is fed to the centrifuge through a stationary tube l) which terminates within feed chamber 55 (Fig. l). The slurry is then accelerated within chamber 55 by means of accelerator 5l" and thrown radially through passages 54, The coarser particles of solids are collected by scroll 4522 and removed directly to the right in Fig. 1. When the solids come in registry with port I3 they are thrown radially therethrough by centrifugal force and collected by means of a hopper (not shown) in the bottom of case I9. Solids which are thrown upwardly impinge on an impeller cover 1| which extends around the upper half `of impeller 12. A secondary scroll 'i3 serves to scrape away any solids which may adhere to cover ll thus permitting them to fall into the hopper.

Returning now to the slurry which is fed into the bowl from passages 54 the partially claried mixture enters the interstices between the discs 52 in each disc stack 5I, whereupon further clarification takes place. The nner particles of solids slide radially outward along discs 62, and the liquid eiiluent emerges from the inner edge of the disc stacks into the axial passages l5. These further separated line particles are collected from the inner bowl face by means of scroll 49a and are scraped gradually to the right in Fig. 1 until they are collected by scroll lllibv and discharged from the centrifuge as described above. The effluent in passages l5 discharges from the bowl through passages I2, l2 whereupon it may be collected in any suitable manner. The construction and arrangement of the disc stacks is designed to facilitate cleaning, it will be understood that these stacks may be readily removed for this purpose by means of clips 64 and screws 65.

In the event that the operator feeds quantities of slurry to the machine in excess of that which may be accommodated through passages 54, such excess will back-up and be discharged through the bore 55 of chamber 55 which bore is of greater diameter than the outside diameter of feed tube i9. This excess slurry will then be fed into the clarification zone by means of radial ports 16 in sleeve 52. In the event that port 'I6 cannot accommodate the excess slurry it will then back-up around the outside of feed tube 'I9 and be discharged from the machine through the sleeve 'll which extends into the conveyer body and is securely attached to collar 'i8 so that there is no danger of slurry reaching bearing I6.

This feature of the construction is important to avoid danger or injury in the event .that excess material is fed. In View of the fact that the present centrifuge is intended for large quantities of material in continuous operation the possibility of excess feeding is more likely than in a batch type machine.

Another important feature of the construction resides in the double taper provided for bowl Il. Portion I la of the bowl is provided with a 1 taper to cooperate properly with the discs and the clarifying section of the centrifuge. Portion IIb of the bowl is desirably provided with a taper to provide efficient removal of the coarser solids. This feature reduces the drying path for the solids considerably.

I have therefore provided a comparatively large volume centrifuge which is adapted to handle a mixture having excess solids in such a way that excellent clarification is provided together with extreme dryness of the separated solids. Heretofore, such results could only be achieved by means of a plurality of centrifuges each designed for one of the above results. In

addition, my improved centrifuge operates eiliciently whetherthe solid contents of the mixture to be treated are of a crystalline, fibrous or granular material.

I claim:

l. A conveyer body weldment for centrifuges comprising a hollow cylindrical body, a cap welded to one end of said cylindrical body, a plurality of radially extending fins welded to the periphery of said cylindrical body, said ns extending axially of the body, a crossbar welded to the outer lateral edge of each n, a plurality of removable discs supported between said ns, and a helical scroll welded to the crossbars and enclosing the body, ns, and crossbars.

2. Apparatus in accordance with claim 1 in which the cap has a hollow feed chamber extending coaxially therewith, la plurality of radially extending feed passages in communication with said feed chamber. a cylindrical sleeve coaxially welded to said cap and enclosing said feed chamber, and a helical scroll welded around the periphery of said cylindrical sleeve.

3. Apparatus in accordance with claim 1 in which the cap has a hollow feed chamber extending coaxially therewith, a coaxial opening on `an end of said feed chamber, a plurality of radially extending feed passages in communication with said feed chamber, a cylindrical sleeve coaxially welded to said cap and enclosing said feed chamber, a plurality of radial ports in said cylindrical sleeve, a helical scroll welded around the periphery of said cylindrical sleeve, and a stationary feed tube extending axially into the opening of the feed chamber and having clearance between the tube and said opening whereby excess mixture will be discharged from the feed chamber into the cylindrica1 sleeve and from thence through the ports in said sleeve.

4. Apparatus in accordance with claim l, in which the cap has a hollow feed chamber extending coaxially therewith, a plurality of radially extending feed passages in communication with said feed chamber, a cylindrical sleeve coaxially Welded to said cap and enclosing said feed chamber, and a tapered helical scroll welded around the periphery of said cylindrical sleeve.

FREDERICK H. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date '748,038 Ayers Dec. 29, 1903 924,376 Phillips June 8, 1909 1,136,256 Noble Apr. 20, 1915 1,885,154 Strezynski et al. Nov. 1, 1932 G0 2,308,559 Winkler Jan. 19, 1943 2,458,706 Howe Jan. 11, 1949 FOREIGN PATENTS Number Country Date 604,329 Germany July 20, 1933 885,165 France Sept. 7, 1943 

